To investigate the role of IL-23 in the progression of a T cell mediated destructive inflammatory arthritis, we induced antigen-induced arthritis (AIA) in WT and IL-23p19 knockout (IL-23p19KO) mice by immunization with methylated BSA (mBSA) in Complete Freund's Adjuvant (CFA) and induced mono-arthritis one week later by a single intra-articular injection of mBSA into the knee joint. The gene discussed is IL23A; the disease is arthritic joint disease.